The herpesviruses are the largest and most complex of the known oncogenic DNA viruses. Three human herpesviruses have been implicated as possibly contributing factors in certain human tumors: Epstein-Barr Virus in Burkitt's lymphoma and nasopharyngeal carcinoma, herpes simplex virus type 2 in cervical carcinoma and cytomegalovirus in Kaposi's sarcoma. The evidence for this rests primarily on epidemiological and serological associations; the long-term persistence of the viruses in a latent reactivable state in neurons and lymphocytes of most individuals and the ability of the viruses to transform normal primary cells into permanently growing or malignant cells in culture. We have been mapping and studying the structure of the large DNA molecules from these viruses with the long term goal of defining the detailed molecular mechanisms of morphological transformation by human herpesviruses. Specific isolated DNA fragments representing 5-10 percent of the HSV-1 and HSV-2 genomes have already been shown to consistently initiate focus formation in monolayers of contact-inhibited cells. In some cases cell lines derived from these foci contain stably integrated fragments of viral genetic information. Under funding of this project we plan to: (1) More precisely define the herpes simplex virus genes responsible for initiating focus-formation; (2) Detect their RNA and protein products in the transformed cells and examine the novel linkage between viral and cellular DNA sequences; (3) Identify a similar small "transforming fragment" from cytomegalovirus DNA on which to concentrate our mapping studies; and (4) Identify the fragment from Epstein-Barr Virus DNA that codes for the EBNA antigen, a consistent viral marker expressed in Burkitt lymphoma cells.